Enlarging treaty ships initially requires an assumption that everything except size stays much the same. In practice, extra displacement changes what designers can build and what navies require from them. A 15,000-ton cruiser might carry four or five triple 8-inch turrets, more aircraft, a different gun layout, or machinery intended for about 40 knots. Those choices would then reshape later cruisers and destroyer leaders, making precise predictions about modern descendants increasingly speculative. The historical basis runs out once too many of those decisions have to be invented.
Notable Point · 2:47:37-2:50:05
Where naval alternate history becomes fiction
One changed treaty limit can support a first-order design estimate, but repeated downstream changes soon outrun historical evidence.